reference global logrus (#274)

* reference logrus' global logger instead of passing and storing a logger reference everywhere

* always directly use global logrus logger instead of referencing an instance

* test suites should also directly use the global logrus logger

* rename gin logging function to clarify that it's middleware

* correct comments which erroneously referenced removed logger parameter

* setting log level for tests now uses logrus' exported type instead of the string value, to guarantee error isn't possible

internal/federation/federatingdb/update.go

@@ -41,13 +41,13 @@ import (
 //
 // The library makes this call only after acquiring a lock first.
 func (f *federatingDB) Update(ctx context.Context, asType vocab.Type) error {
-	l := f.log.WithFields(
+	l := logrus.WithFields(
 		logrus.Fields{
 			"func": "Update",
 		},
 	)
 
-	if f.log.Level >= logrus.DebugLevel {
+	if logrus.GetLevel() >= logrus.DebugLevel {
 		i, err := marshalItem(asType)
 		if err != nil {
 			return err